have picked scratted and pressed some apples, juice is in sterilised demi johns and cider yeast has been added. Now 36 hours later and there has been no activity at all from the apples, they have fermentation locks on and there is no air leaks.

Is this normal? should there have been some activity yet or am I just being premature?

Usually the ferment will start within 24 hours, but if temps are cool it may take longer. Also when you add the yeast you need to sprinkle it on top of the cider so that it rehydrates evenly, just dont dump it in or it will take longer.

Since you are in the UK, I'm assuming that you are using Youngs cider yeast, which is OK, but I'd recommend trying Brupak Ale yeast - it works great for cider